“The value creation should remain in the plant”: Aluminium recycling by centrifugal processing

Professor Reichstein, what problem in current aluminium recycling is the process you are working on intended to solve?

What distinguishes centrifugal treatment from your earlier work on separating Fe-rich phases?

Simon Reichstein: We have tested various physical approaches. These include selective solidification and solidification under centrifugation. When assessing a process of this kind, however, it is not enough to consider whether the separation works from a technical perspective. The achievable efficiency and the technical and economic effort required for implementation are equally important. Taking all of these factors into account, the current approach appears to us to be the most favourable so far.

Can you give us an insight into the current status of your research? What findings have you made so far?

The next step is to transfer the process to a larger scale. We are currently planning to scale up the system at Rauschert Heinersdorf-Pressig GmbH. This will allow us to investigate and optimise, in particular, cycle times and service life of the components under conditions closer to industrial practice.

What are the main technical challenges in moving from the laboratory process to an industrially viable scale?

Simon Reichstein: One of the key issues when scaling up the process will be whether the laboratory results can be transferred to a larger scale. In other words, how will efficiency, impurity levels and cycle times change when we move from batches of around one kilogram to batches of 500 kilograms?

The second key point will be to optimise the degree of automation and the amount of rework required to such an extent that the process becomes economically viable.

For which alloys and scrap qualities is the process suitable, and where are its limits?

Which companies could use the process on an industrial scale, and what benefits could it offer die casting foundries?

Simon Reichstein: The target group is essentially companies that work with molten aluminium and generate the types of scrap mentioned above. The idea is to retain a larger share of the value creation within the plant. Instead of sending the scrap away for external processing, it could be treated directly on site.

This would also eliminate the corresponding transport requirements. With suitable implementation, energy costs could also be reduced. The process is therefore particularly interesting for low-pressure die casting foundries, gravity die casting foundries and sand-casting foundries.

High pressure die casting foundries can benefit as well, although to a lesser extent, as they typically generate smaller quantities of dross. Whether investing in such a system is worthwhile therefore depends, among other things, on the size of the foundry and the actual quantities of material generated. Ultimately, a cost-benefit analysis for each individual operation will have to show whether investing in its own system makes economic sense.

In a later stage of commercialization also wrought aluminum alloys recycling plants can profit from the process. However, due to the larger volumes handled in such plants, further scale-up of the process and corresponding developments are required.